Strategy games are typically board games or video games with a high significance of the players' decision-making skills in determining the outcome.
Many games include this element to a greater or lesser degree, making demarcation difficult.
It is therefore more accurate to describe a particular game as having a degree of strategic elements.

Strategy (and tactics) are usually contrasted with luck, and one can think of games as existing on a continuum from pure skill to pure chance.

Abstract strategy
The game is only loosely tied to a real-world theme, if at all.
The mechanics do not attempt to simulate reality, but rather serve the internal logic of the game.
Chess, checkers, and go are excellent examples.

Simulation
The game is an attempt to capture the decisions inherent to some real-world situation. Most of the mechanics are chosen to reflect what the real-world consequences would be of each player action and decision.
It is problematic to cleanly divide abstract games from simulations, and more accurate to think of games as existing on a continuum of almost pure abstraction (like Abalone) to almost pure simulation (like Strat-o-matic Baseball[?]).

Real-time strategy
Usually applied only to certain computer strategy games, this indicates that the action in the game is continuous, and players will have to make their decisions and actions within the backdrop of a constantly changing game state.
Very few non-computer strategy games are real-time; one example is Icehouse.

Turn-based
The term "turn-based strategy game" (TBS) is usually reserved for computer strategy games in order to distinguish them from real-time games.
A player of a turn-based game is allowed a period of analysis (often infinite) before committing to a game action.
Almost all non-computer strategy games are turn-based.
See also: Civilization series, X-COM

War game
The game is an attempt to simulate an actual or reasonable hypothetical battle. Players will have to consider situations that are analogous to the situations faced by leaders of historical battles.
As such, war games are usually heavy on simulation elements.
Some games of this type will use physical models of detailed terrain and miniature representations of people and equipment to depict the game state.